The capacitor is a critical element in radiofrequency and microwave circuits for high frequency wireless applications.
A metal-insulator-metal (MIM) capacitor is commonly used in high performance applications in CMOS technology. Typically, the MIM capacitor has a sandwich structure and can be described as a parallel plate capacitor. The capacitor top metal (CTM) is separated from the capacitor bottom metal (CBM) by a thin insulating dielectric layer. Both parallel plates are typically formed from Al or AlCu alloys that can be patterned and etched through the use of several photolithography photomasking steps. The thin insulating dielectric layer is typically made from silicon oxide or silicon nitride deposited by chemical vapor deposition (CVD).
Vertical natural capacitors (VNCAP) with stacked via-comb structures have emerged as an attractive option due to their low cost, high density, and highly symmetric configurations.